Bone‑Conduction Fortiphone

The Bone‑Conduction Fortiphone is an early British electrical hearing aid designed specifically for users with middle‑ear deafness, marketed by Fortiphone Ltd. in 1934. The system consists of a compact bone‑conduction receiver worn behind the ear, coupled to a body‑worn amplifier and battery pack. Sound is transmitted directly through the bones of the skull to the inner ear, bypassing the ear canal and middle‑ear structures entirely.

The 1934 advertisement emphasises the device’s ability to reproduce speech, wireless broadcasts, theatre, church services, and “talkies”, with claims of “purity of tone” and “naturalness.” The receiver was promoted as discreet, lightweight, and nearly invisible when worn.

This model represents one of the earliest commercially available bone‑conduction hearing aids, predating the widespread adoption of bone‑conduction transducers in hearing‑aid design by more than a decade. It demonstrates Fortiphone’s early experimentation with alternative transduction methods and their focus on specialised solutions for conductive hearing loss.

Technical Features

• Bone‑conduction receiver worn behind the ear
• Direct‑drive transducer coupling sound to the mastoid region
• Body‑worn amplifier (likely carbon microphone input stage)
• Low‑tension battery operation, compatible with Fortiphone’s own “Fortamax” batteries
• Acoustic bypass of the ear canal and middle ear
• Designed for conductive/middle‑ear deafness
• Discreet form factor for 1930s standards

Physical Construction

• Receiver: small, curved bone‑conduction unit designed to rest discreetly behind the outer ear, with its contact surface positioned against the bone for effective transmission.
• ​Amplifier: pocket‑sized body unit (not shown in advert but typical of the period).
• Battery: external, likely belt‑mounted or pocket‑mounted
• Finish: polished metal or Bakelite‑style casing (typical for Fortiphone products of the era)

Historical Notes

The Bone‑Conduction Fortiphone is significant in the development of hearing‑aid technology. While bone‑conduction principles were known in the 19th century, commercial electrical bone‑conduction hearing aids were rare before the late 1930s. Fortiphone’s 1934 model is therefore an early and notable example of the technology being offered to the general public.

The model was advertised with a free test at Fortiphone’s headquarters at Langham House, 308 Regent Street, London W.1, and a home‑trial offer, indicating active commercial distribution.

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Elenco delle radio e altri apparecchi della Fortiphone Limited; London